A lot depends on if and where you ever plan to travel. One thing to remember is that almost all non-resident permits take time to receive and if you decide to take a trip someplace your not covered with your current permits, you can't pick up a Utah or Florida permit overnight. By my tally, a Utah permit would add:
Wyoming, New Mexico, North Dakota, Minnesota, Alabama, Georgia, West Virginia, Pennsylvania & Delawareto your Washington resident and Oregon non-resident permits.
Besides my Kansas license, I also have New Hampshire and Utah non-resident licenses. Besides reciprocity, two of the best reasons I can think of for having multiple licenses are a renewal hang-up with a license or relocation. If my renewal notice were to be lost in the mail or something, my current permit may actually expire before I am able to get everything straightened out. By having multiple permits, I'm still covered, at least partially. If I were to move out of Kansas, my Kansas license would immediately become invalid. However, the state I move to may have residency requirements that I may have to live there a certain amount of time before being able to apply for a resident license from that state. By having other non-resident licenses already, I will still be covered in several locations and possibly even in the state that I moved to.
When you break down the cost of a license, it's usually pretty small considering how many years they are valid for, usually less than the cost of one box of ammunition per year.